The overall objective of the proposed research is to determine the spatiotemporal gradients associated with the development of dendrites, axonal projections, and boutons of corticostriate neurons located in the orbitofrontal and motor cortices of the dog. The autoradiographic and silver degeneration methods will be used to compare the development of motor corticostriate projections with that of orbitofrontal projections. The Golgi and horseradish peroxidase (HRP) methods will be used to determine the location and dendritic morphology of developing corticostriate neurons. Several electron microscopic (EM) labeling methods (EM-autoradiography, Golgi-EM, EM of interacellular HRP) will be used to determine precisely the pre- and post-synaptic elements involved in corticostriate connectivity at different developmental ages. Overall, this research will provide new and important data on the anatomical maturation of orbitofrontal and motor corticostriate projections and will, for the first time, permit a temporal comparison to be made between the maturational rates of different elements of caudate neurons and those of their cortical afferents.